1. Field of the Invention
The present invention relates to a complex type microscopic device incorporating a scanning electron microscope, and in particular to one which comprises a scanning electron microscope and a microscope having a different magnification but the same observing point from/as those of the scanning electron microscope.
2. Description of the Related Art
A complex type microscopic device for observing a part of an extremely minute sample has been known. For example, Japanese Unexamined Patent Application Publication No. Hei 06-308039 discloses a complex type microscopic device which comprises a foreign particle examining unit to observe a minute sample, a scanning electron microscope to observe a part of the sample, and a moving mechanism moving a stage on which a sample is placed between the optical axis of the examining device and the electron axis of the scanning electron microscope. Such a microscopic device has to make a position where a sample is observed with the examining device coincide with a position where the sample is observed with the scanning electron microscope, so that it needs to include a moving mechanism which can move the stage between two distant points on the optical axis and on the electron axis at such a great accuracy equivalent to a magnification of the scanning electron microscope. However, it is almost impossible to realize such a moving mechanism, and it would be extremely expensive even if it were realized.
In view of solving the above problem, another complex type microscopic device has been developed, which is configured to include a scanning electron microscope and an optical microscope with their respective electron axis and optical axis intersecting with each other on the stage. Japanese Unexamined Patent Application Publication No. 2004-319518, for example, discloses such a microscopic device which comprises a scanning electron microscope having an electron axis orthogonal to the stage, an optical microscope having an optical axis intersecting with the electron axis on the stage, a display unit to display magnified images of a sample obtained with the scanning electron microscope and the optical microscope. This microscopic device is configured so that a moving direction of an image from the scanning electron microscope coincides with that of an image from the optical microscope on the display screen relative to an actual moving direction of a sample. Furthermore, this microscopic device includes a light source emitting a laser light whose optical axis coincides with the electron axis of the scanning electron microscope so that an area of the sample observed with the scanning electron microscope can be observed with the optical microscope by optical spots of the laser light.
However, there still remains a problem in the above complex type microscopic device that due to a large difference in magnification between the scanning electron microscope (20,000 to 30,000 times, for example) and the optical microscope (10 to 100 times, for example), in observing the same sample, an image observed at a magnification of the optical microscope and that observed at a magnification of the scanning electron microscope will be tremendously different in size, for example, a minute point of an image observed with the optical microscope will be a very large area when observed with the scanning electronic microscope. Because of this, it is very difficult to properly observe an arbitrary portion of the image from the optical microscope with the scanning electron microscope since the arbitrary portion of the image from the optical microscope cannot be matched with the image of that portion from the scanning electron microscope in size.